Eighteen patients who underwent a new ligament reconstruction procedure for painful, unstable thumb carpometacarpal joints were studied. The condition was principally of idiopathic or post-traumatic origin. Reconstruction was done only when splinting and anti-inflammatory regimens had failed. Results were directly related to the extent of articular degeneration. Restoration of strength, mobility, and freedom from pain were better if surgery was performed before significant articular damage was noted on roentgenograms. Stages of joint degeneration are described, and the prognosis for ligament reconstruction at each stage is documented.